Fading phenomena in the tactical radio environment

Most of the recent propagation research that has been sponsored in the 1 to 3 GHz frequency spectrum has centered on propagation phenomena in urban settings to support military operations in urban terrain (MOUT) and the development of personal communication systems. There is a dearth of empirical propagation data in this region of the frequency spectrum that is applicable to tactical military operations. The difference in geometry of a "high-low" and a "low-low" path is rather obvious, but what is not so obvious is the difference in propagation phenomena, especially fading characteristics, of the two types of paths. A "high-low" path in an urban area is usually characterized by what is called "Rayleigh" propagation in which there is no direct line-of-sight (LOS). A "low-low" path between two soldiers is usually via a direct LOS propagation path, but with insufficient terrain clearance to support what is called "Gaussian" propagation. This path is called "Rician." This paper reviews Rayleigh, Gaussian, and Rician propagation phenomena; describes the different factors that are associated with each of these three types of propagation; and discusses the research and experimental work that is needed to enable more accurate prediction of Rician propagation loss and expected fading under different environmental (terrain, foliage, weather, etc.) conditions.